Process for the reduction of neutral and acid metal-salt solution



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STATEZE HANS BARDT, OF

FATE-hil SANTIAGO, CHILE.

PROCESS FOR THE REDUGTION F BI EUTBAL AND ACID METAL-SALT SOLUTION.

No Drawing. Application filed November 18, 1924,

This invention has reference to a process of reduction of solutions ofacid or neutral metal salts, by means of which reduction either themetals of said salts are separated out or'a metal salt of a higherdegree of oxidation may be converted into a metal salt of lower degreesof oxidation, while the equivalent amounts of acid may be produced atthe same'time. 7

It is well known to separate metals from their acid or neutral solutionsby treating said solutions with substances containing polysaccharides ata higher temperature and under pressure. The metal, in the caseot theemployment of wood, saw-dust and the like is deposited upon the wood,and it naturally requires a corresponding expenditure of time and labor,in order to separate the metal from the wood or the like. The employmentof wood, moreover, requires the use of correspondingly large reactionves se ls for the reception of the metal salt solution to be reduced andfor the reducing agent. the known process may be considerably 1111-proved and simplified by proceeding in this manner that the substancescontaining the polysaccharides, such as wood, straw, are not employeddirectly as reducing agents, but causing the reagent to be producedtherefrom by a preliminary treatment. This treatment consists insubmitting wood, straw, peat or the like to hydrolysis by heating themin closed containers for several hours at temperaturesranging between120 to 150 degrees C. in the presence of inorganic acids or solutions ofinorganic salts. By this means solutions are obtained which areavailable as reducing agents and particularly adapted for metal saltsolutions and the reduction of the metal salt solution is ef- 'ected bymixing the metal salt solution with the reaction product of thetreatment of wood or the like with acids or salts, after separating saidproduct from the residue, the mixture obtained being first heated to atemperature between 120 to 150 degrees C, at which temperature thereduction proper is caused to proceed, whereupon the temperature isincreased to about 195 degrees C, which causes a carbonization of theextractive substances. The carbonization of the extractive substances iseffected for the purpose of being able to employ the acid remainingafter the separation of the metals Now it has been ascertained thatSerial No. 250,693, and. in Germany March 7, 19%. i

substances for the production of the reduc- 7o .ing agent in closedvessels at a temperature of from to degrees C. requires several hours.In the employment of the solution thereby produced for the reduction ofmetal salt solutions, however, the length of time of the process is ofless decisive importance than the fact that the reaction temperature offrom 120 to 150 degrees C. is reached.

The utilization of the reducing agent separated from the residues of theoriginal material under treatment is likewise out importance in thereduction particularly of metal salt solutions of higher degrees ofoxidation into salts of lower degrees of oxidation, thus for example inthe manufacture of copper-protochloride from solutions of copperchloride. In this case there is no necessity of a separation to beeflected of the products of reduction from the wood residue and thelike.

Emample.l00 kilograms comminuted wood are mixed with 600 liters ofsulphuric acid of about 0.5%, and the mixture is heated in a pressureboiler for three hours 95 to about 132 degrs. C. The solution therebyobtained is added to Q-thousands liters of a 5% copper-sulphatesolution, and both solutions are heated to degrs. C. The copper isthereby precipitated in metallic, crystalline condition, and therecovered solution from which the extractive substances have beenremoved, may serve for the lixiviation of new quantities of metal. Theinvention applies particularly to nonnoble metals. lVhile I have shownand described practically but one embodiment of the invention, it shouldbe understood that it is not restricted thereto, but hat the inventionis broad enough to cover various ill) modifications and changes withinthe scope of the appencletl claims.

I claim:

1. The process of reducing; -opper salt solutions, which comprisestreating cellulose material with inorganic liquors in the ahsence oftree alkali antler pressure, am at temperatures rq'iproximating 120 to odegrees C.. separating the resul ing; liquid from the resitlue aiul thenheating copper salt solutions with such liquitl at temperaturesapproximating" 120 to 150 degrees C.

2. The process of reducing; copper salt solutions. which comprisestreating cellulose material with inorganic acitl reaca'iins liquor underpressure, anrl at temperatures averaging from 120 to 150 (lGjZ'IOOS Q.an l heating the resulting liquitl with copper salt solutions at aboutthe same temperature, antl thereby reducing the metal salt.

3. The-process oi retlucingl tre ting copper salt solutions, Wait-hcempri. digesting cellulose material untler pressure and at temperaturesaveragingfrom 120 to 150 degrees C. with inorganic liquors in theahsence of free alkali, heating" the resulting liquid with copper saltsolutions a' about the same temperature, and thereh reducing the coppersalt, thereupon increasing the temperature to approximate y 195 degreesC, tl erehy carhonizing the organic constitnts, and recovering theresulting 2lCl(l uor. t. The process of retluciiurl v treating coppersolutions. which comprises digesting cellulose material untler pressureand at temperatures averaging from 120 to 150 (legrees C. with inorganicliquors in the ahsence of tree alkali. h ating the resulting liquitlWith copper salt solutions at about the same temperature, thercbredu-iug" .Bttltl metal salt, thereupon heating the reducing liquor \i hthe copper solutions to temperatures averaging 195 degrees C. therehcarhonizing' the organic constituents, I )\-ting the resulting acitlliquor. separating saitl acitl liquor, and extracting ores ainln'ietallic matcria with the same.

In testimony whereof I have sigretl this specification.

ue lit HANS B A R DT.

